Description
TM 9-1546-4 M59, M78, and M79 Telescope Mounts Technical Manual – September 1952
Item Overview
This U.S. Army Technical Manual, TM 9-1546-4, covers the M59, M78, and M79 telescope mounts. Published in September 1952, it was prepared for military personnel responsible for the inspection, adjustment, repair, and maintenance of these precision fire-control components. The manual offers useful period information for collectors, restorers, researchers, and owners of related military equipment.
Identification and Features
The M59, M78, and M79 were mechanical mounts made to hold military aiming telescopes in a stable and adjustable position. Although commonly called telescope mounts, they were working parts of complete sight units rather than simple brackets. Depending on the model, their controls helped a gunner set elevation and direction, level the sight, and keep the telescope aligned with the weapon.
- Official U.S. Army Technical Manual TM 9-1546-4
- Published in September 1952
- Covers the M59, M78, and M79 telescope mounts
- Written for ordnance maintenance and repair personnel
- Relates to mortar, recoilless-rifle, and rocket-launcher fire-control equipment
- Useful reference for identifying parts, controls, and mechanical assemblies
Manual Contents and Coverage
This manual explains the construction and maintenance of the three covered telescope mounts. Its technical material addresses inspection, cleaning, disassembly, repair, assembly, adjustment, and testing procedures. It also helps the reader understand the relationship between the mount, its telescope, level vials, scales, adjustment controls, and related sight-unit parts. The instructions were intended to help maintenance personnel return damaged or inaccurate equipment to proper working condition.
Historical Background
TM 9-1546-4 was issued during the Korean War, when the U.S. Army still operated large amounts of World War II equipment while adding newer postwar weapons. Accurate fire-control instruments required specialized care because dirt, wear, impact damage, or poor adjustment could cause serious aiming errors. By placing the M59, M78, and M79 in one maintenance publication, the Army gave ordnance personnel a common reference for several related sighting systems then found in active units, training commands, and maintenance facilities.
History of the Telescope Mounts
Military telescope mounts connected an optical sight to a weapon while allowing controlled movement for elevation and direction. The M59 was associated with the M27 sight unit used on the M2 4.2-inch chemical mortar. The M78 worked with the M85C telescope on the M20 75mm recoilless rifle. The M79 became part of the M34-series sight units, which commonly combined the mount with an M62-series elbow telescope and a telescope adapter. These rugged mounts used mechanical controls, graduated scales, and level vials so crews could establish and repeat accurate settings under field conditions.
Associated Weapon Systems
The mounts covered by this manual supported several important American weapon systems. Their use ranged from high-angle mortar fire to direct-fire recoilless rifles and later rocket-launcher applications. Each mount provided the stable and adjustable base needed to turn range and direction data into a usable weapon setting.
- M59 Telescope Mount: Used with the M27 sight unit for the M2 4.2-inch chemical mortar, a heavy rifled mortar that delivered high-explosive, smoke, and chemical-agent ammunition.
- M78 Telescope Mount: Paired with the M85C telescope for the M20 75mm recoilless rifle, a crew-served weapon used for direct fire against vehicles, fortifications, and troop positions.
- M79 Telescope Mount: Used in M34-series sight units with the M62 elbow telescope. This sight family supported weapons that included the M20 75mm recoilless rifle and the M21 4.5-inch multiple rocket launcher. Later applications also included mortar systems such as the M29 81mm mortar and the M84 self-propelled 4.2-inch mortar.
History of Use
The M2 4.2-inch mortar served American forces during World War II and remained an important heavy infantry-support weapon during the Korean War. The M20 75mm recoilless rifle entered service near the end of World War II and saw extensive use in Korea, where its mobility and direct-fire power made it valuable to infantry units. M79-based sight units continued in later Cold War service on recoilless rifles, mortars, and rocket equipment. In each application, correct maintenance of the telescope mount was necessary to preserve smooth movement, accurate level readings, and proper alignment between the sight and weapon.
Ideal For
This September 1952 manual is a useful addition to collections focused on U.S. Army ordnance, military optics, artillery fire control, infantry support weapons, the Korean War, and early Cold War equipment. It can also help museums and restorers identify period components and understand how these sighting mounts were maintained.
- U.S. military manual collectors
- Korean War and early Cold War historians
- Military optics and fire-control collectors
- Mortar and recoilless-rifle researchers
- Museum displays and restoration projects
- Historic ordnance reference libraries
Approx length 6", Approx width 9", Approx height .25", Approx weight .5lbs.
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